Okay, I have to ask. What are Scrow? Even Google can't help me with this one.
Or is it just a poll thing to see how many people will vote for a race they don't even know?
How are tieflings and aasimar setting specific?
Yes they're somewhat iconic in 2e Planescape, but they appeared in the 3e core MM and later in the 3e FRCS as a standard PC race not just a "monster". Then the tiefling (at least in name if not at all in appearance) showed up as a core 4e race. Both are PC races in Pathfinder.
Changelings?
Good catch. But Changelings I think should be optional - a race of freely shapeshifting people has massive world-design implications.